noun
Mathematical term for the length of the boundary of a closed shape. 周長 is the general term for perimeter; for circles, 円周 is more common.
この長方形の周長を計算してください。
Please calculate the perimeter of this rectangle.
円の周長は直径に円周率をかけて求めます。
The circumference of a circle is found by multiplying the diameter by pi.